The present invention relates to white-pigmented polymers (particularly, polyolefins such as polyethylene) containing white pigments treated with an organosilicon compound to improve processibility in compounding and improve performance properties such as lacing resistance in a polyolefin matrix.
Treatment of TiO.sub.2 pigment with organosilicon compounds to improve dispersibility in a polymer matrix is well known in the art. For example, U.S. Pat. Nos. 4,061,503 and 4,151,154 disclose enhanced dispersibility of TiO.sub.2 in paints and plastics. Therein, the TiO.sub.2 is surface treated with a silane possessing at least two hydrolyzable groups bonded to silicon and an organic group containing a polyalkylene oxide group.
In addition, U.S. Pat. No. 4,810,305 discloses a modified hydrophobic pigment or filler containing 0.05 to 10 weight % of an organopolysiloxane, with improved dispersibility in synthetic resins.
However, deficiencies in the prior art include, but are not limited to, (1) unacceptable processibility, i.e., dispersibility of TiO.sub.2 pigment in a polymeric matrix at slow rates; and (2) lacing, i.e., development of imperfections in a polyolefin matrix. Lacing occurs as a result of volatiles released from the pigment during high temperature polyolefin fabrication processes. Lacing may also be attributable to TiO.sub.2 concentrates picking up moisture. A further disadvantage is that higher loadings of TiO.sub.2 pigment in a polymer concentrate result in slower processing rates.
It has been found that the above combined disadvantages of the prior art can be overcome by the present invention.